In the existing data interaction process, the security of data is achieved by encrypting the data to be transmitted at a transmitting end and decrypting the data at a receiving end. Almost all encryption system relies on the unpredictability and unrepeatability of keys, and numbers featuring the unpredictability and unrepeatability of keys are generated by a Random Number Generator (RNG).
The existing RNG technologies mainly include noise amplifying technology, analog unsteady state technology and oscillator sampling technology. According to the noise amplifying technology, random numbers are generated by amplifying noises, such as thermal noises or flicker noises; according to the analog unsteady state technology, random numbers are generated by converting unsteady analog signals with an Analog-Digital Converter (ADC). Both technologies are complicated and require high cost in design.
According to the oscillator sampling technology, two oscillators of different frequencies sample each other to generate random numbers, which requires fewer devices, smaller size on chips and lower cost. FIG. 1 shows a common oscillator sampling based random number generating circuit, including Noise Source 11, Amplifier (AMP) 12, Low Frequency Voltage-Controlled Oscillator (L-Freq KVCO) 13, High Frequency Oscillator (H-Freq Osc) 14 and D-type Flip-flop (DFF) 15.
Noise Source 11 is used for generating thermal noises or flicker noises, which are amplified by AMP 12 to create a frequency control voltage applied to L-Freq KVCO 13. The frequency of L-Freq KVCO 13 keeps on changing at random under the control voltage. The output of L-Freq KVCO 13 serves as a clock input of Flip-flop 15 while the output of H-Freq Osc 14 serves as the data input of Flip-flop 15. The output of L-Freq KVCO 13 samples the output of H-Freq Osc 14 to obtain random numbers.
However, limited by Noise Source 11, the random number generating rate of the above circuit is far lower than 1 Mbps and cannot meet the demand of a system which transmits data in a higher rate at present.